Despite the importance of fully functional joints for movement and balance, there are instances in which the pain that can be generated by certain pathologies justify fusion in order to alleviate on-going pain. It is sometimes necessary or desirable to cause fusion or arthrodesis of the bones that form the support structure of the lower leg or hand, for example, in the case of osteoarthritis, post-traumatic osteoarthritis, ankle arthritis or after failure of previous surgical intervention. Arthrodesis fuses the bones of the joint completely, making one continuous bone, and are used to treat conditions in the lower leg and hand, including the hind-foot, ankle, mid-foot, and phalanges.
In accordance with the prior art, fusion surgery involves debriding adjacent bone segments, aligning them as desired and using pins, plates and screws, or rods to hold the bones in the proper position while the joint(s) fuse. Sometimes, the surgeon will add natural or artificial bone graft in order to assist the fusion process. The surgeon may use graft from the patient (a piece of bone, taken from one of the lower leg bones or the wing of the pelvis) to replace the missing bone. If the alignment of the bone is improper, or if the patient is at risk or is non-compliant and uses the joint before it is fully healed, the bones sometimes fuse into a position known as “mal-union”. In more severe instances, the bones do not fully fuse which results in “non-union”. There are two types of non-union; fibrous non-union, and false joint (pseudarthrosis). Fibrous nonunion refers to fractures that have healed by forming fibrous tissue rather than new bone. Pseudarthrosis refers to non-unions in which continuous movement of the fracture fragments has led to the development of a false joint.
Prior art hardware for use in arthrodesis includes wires, screws, plates and intramedullary devices. While such devices exist, each is lacking in providing one or more of the desired precision, stability, fixation, or relative ease of implantation that an orthopedic surgeon desires for such a device. Super-elastic and shape memory bone staples provide an answer to many of these issues, but a more desirable method of storage and insertion represents an improvement over the prior art.
Thus, it is an object of the present invention is to provide a bone fusion system and surgical method for implanting an implant in a mammal (including specifically humans, and domestic pets and livestock, like horses, cattle, sheep, goats, dogs, and cats), which allows for fusion of the bones or bone segments in particular of an extremity. The method includes using an incision to access the bone or bone segments to be fused, debriding and aligning the bones or bone segments, selecting a bone staple of the proper size, mounting a bone staple from a storage block on an inserter by engaging the staple with the tips of the inserter and aligning the handle of the inserter to cause the legs of the staple to splay into an open position orthogonal to the web of the staple which disengages the storage block. Further in this method, a slide inhibits the inserter legs from returning to the un-splayed position while the staple is in position on the inserter so that the staple can be tamped into the adjacent bone using the inserter to transmit the force. (Without such a provision, the legs would immediately assert a force to return to the un-splayed position such that implanting the staple becomes increasing difficult as the legs move out of the orthogonal positions.) When the staple is in position in the bone so far as possible using the inserter as a combination holder/tamp, the locking slide is repositioned so that the handles can be returned to the open position and the staple can be disengaged from the tips of the inserter. The inserter includes a section of the handles, which allow the staple legs to be implanted in the bone or bones by tamping the handles and transmitting the force to the staple to anchor it in the bone or bones. The staple can be tamped further into the bone as necessary, and the wound can be closed. In some instances a further tamp is used to implant the staple into a position in which the staple web is as close as possible to (i.e. at or below) the bone surface.
The staple will subsequently apply a compressive force (parallel to the web member) to the adjacent bone segments to press them into contact as the staple legs act to return to an unsplayed position in which the staple legs are at an angle of less than 90° relative to the staple web or bridge.